Java Heap Memory error

Question

I am getting this error:

Exception in thread \"main\" java.lang.OutOfMemoryError: Java heap space
    at com.mysql.jdbc.MysqlIO.nextRowFast(MysqlIO.java:1585         


        

Answer 1

When you query returns very large sets, the mysql driver will by default load the entire result set in memory before giving you control back. It sounds like you're just running out of memory, so increase the memory furter, e.g. -Xmx1024M

The other alternative might be to enable streaming results on your MySQL queries- this prevents the entire ResultSet to be loaded into memory all at once. This can be done by doing

stmt = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY, 
           java.sql.ResultSet.CONCUR_READ_ONLY);//These are defaults though,I believe
stmt.setFetchSize(Integer.MIN_VALUE);

(Note that anything else but Integer.MIN_VALUE has no effect on the MySQL driver)